Engine starting mechanism



Oct. 27, 1942. R. M. NARDoNE ENGINE STARTING MECHANISM Filed Dec. 26,1940 a i W i l .l 1

www swuu.. a my# WE Patented 27, 1942 UNITED STATES PATENT OFFICE ENGINES'IAR'EIING MECHANISM Romeo M. Nardone, Westwood, N. J., assignor toBendix Aviation Corporation. South Bend, Ind., a corporation of DelawareApplication December ze, 1940, semi No. 371,846

4 Claims.

This invention relates to starting mechanism for internal combustionengines, and particularly to mechanism wherein there is incorporated anelement that is adapted to impart initial rotary movement to the engineby actual engagement with a rotatable part thereof.

One of the objects of this invention is to provide a novel method of andmeans for protecting the starter parts from the adverse eiects thatmight otherwise be produced by a back-fire," or premature ignition ofthe engine to be started.

Another object of the invention is to provide additional improvements inthe type of engine starter disclosed in my Patent No. 2,144,196 grantedby the United States Patent Oflice on January 17, 1939, the nature andscope of which improvements are indicated in the accompanying drawingand the following particular description of one form of mechanismembodying the invention. It is to be understood, however, that thedrawing is for the purpose of illustration only, and is not designed asa definition of the limits of the invention, reference being had to theappended claims for this purpose.

In the drawing,

Fig. 1 is a longitudinal sectional view of a device embodying theinvention;

Fig. 2 is a transverse view along line 2-2 of Fig.v1; and

Figs. 3-7 are diagrammatic views showing the several stages of ratchetaction during a backfire."

With reference to the drawing, and more particularly to Fig. 1, theengine starting mechanism is contained within a sectional housingincluding cylindrical parts Il and I0, the latter having a ilange I2 bywhich it is secured to an engine crankcase I3 as by bolts I4, the flangebeing conveniently of a size stardardized for aircraft engine starters.The engine crankshaft, or other drive shaft (not shown) is provided witha clutch-element I I engageable by the piston actuated clutchelement I5as will be later more fully described.

Cylinder Il has a head end I8 and a crank end 23, the latter being shownas an integral part of a splined tube 2I. Slidably fitted within thecylinder Il is a piston 23 movable with a hollow internally andhelically grooved screw 24 which is externally splined as at 23, tocooperate with the internally splined tube 2|. erating grooves 23 and 28are placed a series of friction reducing members shown as balls 21assembled in a cylindrical cage, the end rows of balls having theirsurfaces engageable with plates Between the coop- 28 located at each endof the splined grooves to 55 facilitate free rolling movement of theballs which they engage at points spaced above or below the mid-planethereof, and also to hold the. cage against more than a predeterminedendwise movement. A second screw 22 is drivably connected with the screw24 by helical grooves or threads 28 and 30 which permit the axial travelof the piston 23 but cause rotation of the screw 22 because of frictionreducing balls 38 inserted in the helical grooves 28 and 30. A spring 31has one end resting against the closure plate 28 of the cylinder I1, andits opposite end abuts the thrust ring 38, which is, in effect, theouter race of a ball bearing assembly 40 axially movable with butrotatably free of the piston 23, the intervening bearing balls 40facilitating free rotationA of outer race 38 of the bearing, the outerrace being possibly constrained to rotation by the natural twistingtendency of a spring such as the spring 31, as the latter is compressedin the forward travel of the piston. Piston rings 38 insure against theloss of pressure as the piston moves forward, and also yieldably opposerotation of the piston, even though twisting of spring 3l shouldoccasionally cause outer race 38 to rotate to some extent.

Due to the bolted split clamp connection 4| between the cylinder Il andthe body flange I8, the former may be quickly detached for removing anyfouling that may occur where combustible cartridges are used as thesource of fluid pressure to move the piston 23.

An exhaust valve 42 is shown as cooperating with an exhaust port 43conveniently formed in the housing 44, and communicating with an exhaustconnection 45 leading to any desired point. In the case of an airplane,for example, this exhaust connection will lead to a point exteriorly ofthe fuselage. The valve 42 is carried by a stem 48 which is of such alength that with the piston in its position as indicated in Fig. 1, aspring I8 will bear against an enlarged head 52 on the stem 48 to holdvalve 42 closed. At the commencement of an operative cycle of the motor,such as is occasioned by the delivery of fluid pressure to the chamberformed by the neck-portion 58 of the housing I8, this fluid pressurewill act upon the head portion of the valve 42 insuch manner as toassist the spring 48 in maintaining the said exhaust valve 42 closed;but as the piston nearly reaches the end of its movement, a collar 53extending inwardly of piston 23 and surrounding the stem 48 will bebrought into engagement with the head l2 and, will be eilective tounseat the exhaust valve 42. The exhaust valve having been gagement withthe engine member II.

unseated in the manner described, the spring 48 will be effective forholding it in open position, its maximum opening movement being limitedby a longitudinally slotted cylindrical stop 54 having a flange 66abutting the end vsurfaces of the ngers 61 (shown in transverse sectionof Fig. 2) formed by longitudinally slotting the neck-portion 56 of thehousing I8. This neck-portion 56 is externally threaded, as shown at 68,to receive the housing 44, the latter being screwed up on the threads 68until surface 69 of the housing 44 abuts the flange 66 of the stop 54and with the inlet passage 45a aligned with the longitudinal slotsbetween fingers 61. Stop 54 is adapted to be rst slipped over the valvehead 42; and due to the eccentricity (indicated at 50 in Fig. 2) oftheapertured portion of the base 1I of the said stop, the said base hassuiiicient surface remaining to constitute a stop or abutment for valvehead 42 in the open position of the latter, while at the same time beingapertured suiciently to permit insertion and withdrawal over said valvehead.

The piston having `completed its operative stroke, and the exhaust valvehaving been opened, the piston will be urged on its return stroke by thecoil spring 31. During this return movement, the exhaust Valve beingheld open, the cylinder will be effectively scavenged. Due to the actionof the spring 48 the valve will remain open until such time as thepiston collar 53 is brought to bear against the valve stem 41 for againseating the valve. This insures closing movement of the valve at thetime the piston has substantially completed its return movement, theclosing being initiated and assisted by the action of the spring means49 above described. There is thus provided automatically controlledexhaust means, which exhaust means is of such construction as to remainopen during the major portion of the return stroke of the piston so asto insure substantially complete scavenging, as more fully explained inmy Patent No. 2,197,155, granted April 16, 1940.

By reason of the action of spring-pressed balls 51 and 58 upon grooves59 and 60, respectively, in sleeve 22, the initial \axial movement ofthe piston 23 will be transmitted to said sleeve 22, and the axialthrust thus imparted to jaw I5 (through spring 82 surrounding rod 83)will establish en- Upon such engagement the resulting resistance tofurther axial travel will cause, ilrst, a commencement of rotation onthe part of sleeve 22, and secondly, a slipping of the balls 51 and 58from the grooves 59 and 68, so that they may be free to ride along theinner bore of the sleeve 22 as the piston continues forward.

The means for protecting the starter from the effects of a back-nre willnow be described. On the skirt 84 of engine engaging member I5 there issecured a ratchet-tooth clutch element 86, constituting one of a series,the others being shown.

before any movement of the piston 28, and therefore it is the same asthat of Fig. 1.

From this position the engine-engaging member I5, with its integralskirt 84 carrying the clutch element 86, moves forward to engage theengine member II in response to the iirst movement of the piston 23 asheretofore explained. When this engagement is complete the ratchet teethof clutch element 86 will have assumed the relationship, with respect tothe adjacent clutch element 88, that is indicated diagrammatically inFig. 4. With the parts in this relationship, cranking of the enginebegins, the direction of rotation being such as to cause the teeth ofclutch element 86 (and hence the clutch element 88) to move in thedirection of the vertical arrows in Figs. 4 and 5. Now as clutch element81 is held against rotation, as heretofore explained, there willnecessarily be a ratcheting or camming action as between the elements 81and 88, which camming action will shift the clutch element 88Y to theright and therefore into closer mesh with the clutch element 86 by whichthe element 88 is being rotated. This closer relationship is illustrateddiagrammatically in Fig. 5, and this is the relationship of the partsduring the entire period of the cranking action under normalconditionsthat is, in the absence of a "back-nre of the engine beingstarted. On those occasions, however, when such a back-nre occurs, therst eifect thereof is to reverse the direction of rotation of the engineengaging member I5 and thereby cause some rotation of the clutch element86 in the direction of the vertical arrow in Fig. 6. This reversalproduces a new camming action as between the engaged teeth of theelements 86 and 88, which camming action, taken in conjunction With theaction of the spring 9I, results in a leftward movement of the element88 into a condition of complete mesh with the stationary clutch element81; in other words, the parts assume the relationship of Fig. 6, inwhich relationship the element 88 is held against further movement inthe direction in which the clutch element 86 isnow moving and thereforethe former operates to move the clutch element 86 (hence theengineengaging member I5) further to the right, or in other words, intoa relationship indicated diagrammatically in Fig. '1, in whichrelationship the engine-engaging member I5 has been completely withdrawnfrom contact with the teeth of the engine member II; and as suchcomplete withdrawal will of course occur at a time when theengine-engaging member I5 has rotated backward only a relatively fewdegrees from the position at which the reversal of direction of rotationoccurred, it follows that no substantial reverse impack is imparted tothe starter mechanism, such as might be the case if the reversal ofdirection were prolonged until the entire effect of the backiire of theengine had been absorbed. Instead of such entire absorption of back-lireimpact by the starter, the latter is now free and clear of the reverselyrotating engine member, so that the major force of the back-lire willhave been expended before the engine-engaging member I5 is againadvanced into engagement with the engine member II by reason of thecontinued application of pressure to the piston 23-assuming that the`fluid is still being admitted to the piston and that the piston has notyet reached the forward limit of its stroke. If, however, the full forceof the back-fire has not been expended by the time the engine-engagingmember I5 reengages the engine member II, there will be a.

repetition of the automatic withdrawing action abovedescribed, to befollowed by a new re-engagement; such cycle continuing until the piston23 has completed the cranking stroke. Upon such completion, the spring3l will operate to return the piston 23 to its initial position andbring about an exhaust of the operating uid by reason of the functioningof the exhaust valve 42 in the manner explained more fully in my PatentNo. 2,197,155 above identied.

Although the invention has been. explained herein by showing the effectthereof when applied to an engine starting mechanism of the fluidactuated type, it will be apparent that the invention may also beembodied in engine starters of diierent construction and utilizing othersources of energy. Thus, for example, engine starters of the directcranking and inertia type as shown, respectively, in my Patents No.1,926,913 and No. 2,156,667-both of which embody engine engaging memberssimilar to the engine-engaging member I5 of Fig. 1 of the presentdisclosure-could have incorporated therein mechanism embodving thepresent invention, in'which case the engine-engaging member would bemodied to carry a ratchet element corresponding to the ratchet element8B of the present disclosure, and there would be provided in associationtherewith additional ratchet elements constructed and arranged tooperate as do the ratchet elements 81 and 88 above described.

Whatisclaimedis:

1. In an engine starter, in combination, a start` ing means having anaxiallymovable, rotatable Aengine engaging member, means for drivingsaid engine-engaging member, said driving means including a secondaxially movable member, a compression spring interposed between said twomembers, a clutch element rotatable with said engine engaging member,means engageable with said clutch element to move said engine engagingmember axially in a direction away from the` engine engaging position inresponse to a sudden increase of resistance to cranking resulting from aback-nre or the like, and fluid pressure ac-v tuated means constantlyexerting pressure upon said compression spring to urge said engineengaging member back to engine engaging position during the back-nreperiod.

2. In an engine starter, in combination. a starting means having arotatable engine engaging member, means for driving said engine-engagingmember, said driving means including a second axially movable member, acompression spring.

ber back to engine engaging position during the I back-fire period.

3. In an engine starter, in combination, a starting means having anaxially movable, rotatable engine engaging member, means for drivingsaid engine-engaging member, said driving means iny cluding a secondaxially movable member, a compression spring interposed between said twomembers, a clutch element rotatable with said engine engaging member,means engageable with said clutch element to move said engine engagingmember axially in a direction away from the engine engaging position inresponse to a sudden increase of resistance to cranking resulting from aback-nre or the like, and means constantly exerting pressure upon saidcompression spring to urge said engine engaging member back to engineengaging position during the back-tire period.

4. In an engine starter, in combination, a starti ing means having arotatable engine engaging member, means for driving said engine-engagingmember, said driving means including a second axially movable member, acompression spring interposed between said two members, a clutch elementrotatable with said engine engaging member. means engageable with saidclutch element to move said engine engaging member in a direction awayfrom the engine engaging position in.

response to a sudden increase of resistance to cranking resulting from aback-tire or the like,

and means constantly exerting pressure upon said compression spring tourge said engine engaging member back to engine engaging position duringthe "back-fire period.

ROMEO M. NARDONE.

